The present invention relates to a radiation-sensitive composition used in the field of micro-machining technique, a microlithographic process using the same and a method for fabricating an electronic device, particularly a semiconductor device, which comprises said microlithographic process.
Photolithographic techniques forming a micron-order or submicron-order fine patterns have played a core role of micro-machining technique used for the mass-production of electronic devices. The needs toward a higher degree of integration or density of the recent electronic devices, particularly semiconductor devices have led the micro-machining technique to highly progress. Particularly, as the minimum possible machining dimension has been micronized, the photolithographic technique has been increasingly developed with shortening in a wavelength of a light source from g-line (436 nm) and i-line (365 nm) of a high pressure mercury lamp to KrF excimer-laser (248 nm). With respect to a photoresist, a material thereof has changed with changes in the exposure wavelength. Although photoactive compounds or photosensitivity mechanisms are different from one another, an aqueous alkali development making use of solubility of a resin or high molecular material having a phenol structure to an aqueous alkali has been industrially used for the photoresist corresponding to respective wavelengths. Said resin or high molecular material contains a lot of aromatic rings, which have been chemically required from a viewpoint of improving etching resistance in a dry etching step carried out after formation of a resist pattern. Refer to: Elsa Reichmanis, Larry F. Thompson, Polymers in Microlithography; ACS Symposium Series 412; American Chemical Society: Washington, D.C., 1989; P. 1.
As a negative resist of the phenol structure-carrying resin, there are resists of a cross-linking type as disclosed in JP-A-62-164045 (U.S. Pat. No. 5,034,304) and those of a dissolution inhibition type as disclosed in JP-A-4-165359. In any case, submicron-order fine patterns can be formed with no swelling.
In recent years, as the photolithography wherein the minimum possible machining dimension is in a range of much more smaller than 0.25 xcexcm, that using a light source of ArF excimer-laser (193 nm) has been greatly expected. However, said wavelength corresponds to the absorption maximum of the aromatic rings. Accordingly, in case of using the phenol structure-carrying photoresist material so far industrially used, it has been difficult to form fine resist patterns through the aqueous alkali development, because a latent image has restrictedly formed only on an extreme surface of the photoresist film. Refer to: J. Photopolym. Sci. Technol. 6(4), 473-490 (1993).
On the other hand, there have been proposed various resist materials having high dry etching resistance as well as high transmittance within said wavelength range. As a chemical structure other than the aromatic rings, which structure is capable of imparting the dry etching resistance to the resist materials, and which is transparent within a far ultraviolet region comprising the wavelength 193 nm of ArF excimer-laser, JP-A-4-39665 and JP-A-5-265212 disclose use of an adamantan structure, and JP-A-5-80515 and JP-A-5-257284 disclose use of norbornane structure. In addition to these structures, JP-A-7-28237 and JP-A-8-259626 disclose that an alicyclic structure such as a tricyclodecanyl group is generally effective.
With respect to a resist material, which is a high polymer having a chemical structure transparent within a far ultraviolet region comprising the wavelength 193 nm of ArF excimer-laser, and which is usable for the aqueous alkali development, it has been attempted to use a carboxylic acid structure of acrylic acid or methacrylic acid, as disclosed in JP-A-4-39665, JP-A-4-184345, JP-A-4-226461 and JP-A-5-80515. According to these attempts, the carboxylic acid structure of acrylic acid or methacrylic acid serves for solubility to the aqueous alkali as a portion soluble in a developer for the aqueous alkali development. Further, JP-A-8-259626 discloses a high molecular compound formed in a manner such that a carboxylic acid group is attached to an alicyclic structure introduced to a side chain of a methacrylic acid ester.
The phenol structure so far used as the alkali soluble group shows 10.0 of pKa (phenol). Whereas, aforesaid carboxylic acid structure shows a lower value, namely 4.8 of pKa (acetic acid), which means a high acidity. Therefore, in case of using such a carboxylic acid structure for a base resin as the alkali soluble group, rather a resin having such a carboxylic acid structure generally exhibits a large dissolution speed in an aqueous alkali, so long as a molar ratio is the same, and dissolves even in an alkali developer of a low concentration, in which a resin having a phenol structure does not dissolve. Refer to: Pine, Hendrickson, Cram, Hammond Organic Chemistry, Fourth Edition, P. 207.
In case of using the resin having a carboxylic acid as mentioned above, there has been left a problem such that when a cross linking agent as disclosed in JP-A-62-164045 is used, a high acidity carboxylic acid remains on a cross-linked portion, which is therefore subjected to penetration of an alkali developer, thereby causing swelling, and as a result, submicron-order fine patterns cannot be formed. Further, in case of using those capable of forming a compound having a dissolution inhibition action by an acid generated by exposure as disclosed in JP-A-4-165359, there has been left a problem such that the resin having a carboxylic acid gives no dissolution contrast and provides no negative resist.
On the contrary, JP-A-11-109627 discloses a method for forming a non-swelling negative pattern, which uses a phenomenon such that a hydroxycarboxylic acid structure changes to a lactone structure through intramolecular esterification by an acid-catalyzed reaction. The hydroxycarboxylic acid structure is effectively esterified in the molecule by acid-catalyzed reaction, thereby forming a lactone structure. As a result, a number of the carboxylic acid greatly decreases. Therefore, it is quite different from a cross-linking reaction occurring between molecules and showing almost no change in numbers of a carboxylic acid between an exposed portion and an unexposed portion. In conclusion, a developer is hard to penetrate in a portion insolubilized by exposure, and it is possible to control swelling of a pattern after development, which is a problem of a prior art.
With respect to the above-mentioned negative resist using lactonization, JP-A-2000-56459 reports use of a polymer of an xcex1-substituted acrylic acid ester having in its ester moiety a group capable of forming an ester in the molecule through the lactonization. Further, JP-A-2000-352821 reports use of a polymer of an acrylic acid ester or methacrylic acid ester having in its ester moiety a xcex4-hydroxycarboxylic acid-carrying androsterone structure.
According to the above-mentioned negative resist using lactonization, the hydroxycarboxylic acid is effectively lactonized at an exposed portion, thereby greatly decreasing the number of carboxylic acid. As a result, a developer is hard to penetrate in a portion insolubilized by exposure, and swelling of a pattern after development, which is a problem of a prior art, can be controlled. However, even according to the above-mentioned system decreasing the carboxylic acid, in the formation of fine patterns of a 0.12 xcexcm level, which has been required for the pattern formation in the field of ArF excimer-laser, there have been left problems such that penetration of a developer cannot be controlled completely, thereby causing swelling, and a resist film remains between lines of the pattern. As a result, a pattern having a good shape could not be obtained.
An object of the present invention is to provide a radiation-sensitive composition capable of forming a high resolution pattern, which is freed from causes of resolution deterioration such as swelling owing to a permeation of a developer and residual of a resist film between lines of the pattern as mentioned above. Another object of the present invention is to provide a method for forming a negative pattern using such a radiation-sensitive composition. A further object of the present invention is to provide a method for fabricating a semiconductor device using such a pattern-forming method.
Incidentally, the present invention is not always based on the assumption that the above-mentioned prior art is used, and the present invention by no means denies the prior art.
The present invention provides a method for fabricating a semiconductor device, which comprises:
the step of arranging a semiconductor substrate;
the step of coating a radiation-sensitive composition containing a polymer of an acrylic acid ester having a xcex3-hydroxycarboxylic acid in its ester moiety on the semiconductor substrate, thereby forming a coated film; and
the step of irradiating the coated film with an actinic radiation, thereby forming a semiconductor circuit pattern.
The present invention further provides a method for fabricating a semiconductor device, which comprises:
the step of forming a first insulation layer on a substrate;
the step of forming an electrically conductive layer on the first insulation layer;
the step of forming a resist film comprising a polymer of an acrylic acid ester having a xcex3-hydroxycarboxylic acid in its ester moiety on the electrically conductive layer;
the step of subjecting the resist film to a light exposure and a development, thereby forming the resist film into a desired shape;
the step of removing a region of the electrically conductive layer where the resist film is not formed; and
the step of forming a second insulation layer.
The present invention further provides a method for fabricating a semiconductor device, which comprises:
the step of forming a first electrically conductive layer on a substrate;
the step of forming an insulation film on the first electrically conductive layer;
the step of forming a positive resist film comprising a polymer of an acrylic acid ester having a xcex3-hydroxycarboxylic acid in its ester moiety on the insulation film;
the step of subjecting the positive resist film to a light exposure and a development, thereby forming an aperture in the positive resist film;
the step of removing the insulation film naked at the aperture of the positive resist film, thereby exposing the first electrically conductive layer; and
the step of forming a second electrically conductive layer to be connected with the first electrically conductive layer.
The present invention further provides a method for fabricating a semiconductor device, which comprises:
the step of forming a first film on a substrate;
the step of forming a resist film comprising a polymer of an acrylic acid ester having a xcex3-hydroxycarboxylic acid in its ester moiety on the first film;
the step of subjecting the resist film to a light exposure and a development, thereby forming a resist pattern having a minimum dimension W1;
the step of forming a second film on the substrate;
the step of forming a resist film using a resin having a phenol structure on the second film; and
the step of subjecting the resist film to a light exposure and a development, thereby forming a resist patter having a minimum dimension W2, which is larger than said W1.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.